no, i think he was being a friend when putting the blanket on her
In fact, I think that they are cousins.
but it said, "so stupidly dense" and she wouldn't be dense if it's just a friend being caring towards her like usual
http://www.mangago.me/read-manga/nukoduke/bt/6984e5cb7b5429fa/Ch101/pg-5/
Agree~
It could be "defenseless" since she was sleeping in a school library. The japanese language is pretty tricky.
But cousins can legally marry there....
Wait! Was Yamato in love with Inori???